When opening and closing doors, there's visible stuttering that's measurable with the F3+Alt menu.
(Also, I think the F3 menu should be upgraded... It only shows the average FPS, however, this makes it ignore stuttering. You could have bad stuttering, but because 144FPS renders more frames faster than 30 FPS, it reports a number closer to 144FPS. I'd recommend having the F3 menu also report the lowest FPS, so stuttering is also somewhat accounted for in screenshots/recordings.)